Process for making diamonds

ABSTRACT

Apparatus and process for the production of diamond is disclosed. The apparatus includes an exponential horn tapering from a large end to a small end. A copper plate is mounted against the large end of the horn and a magnetic hammer abuts the copper plate. The magnetic hammer and copper plate function to create a shock wave in the exponential horn. An anvil having a small pocket formed therein is mounted adjacent to the small end of the exponential horn so that the small end rests in the pocket. The anvil, horn and hammer are all secured together by bolts or other suitable means and, in operation, graphite is placed in the anvil pocket. The magnetic hammer generates a shock wave in the exponential horn and because of the horn shape, which is critical, the velocity of the shock wave is amplified and the shock wave energy concentrated so that all of the energy in the shock wave arrives simultaneously at the small end of the horn. This energy is transferred to the graphite in the anvil pocket and results in pressure and temperature levels that causes the graphite to be transformed, in part at least, to diamonds.

ilnited States Patent 1 Rasquin et al.

[ 1 3,714,332 [451' Jan.30,1973

I54] PROCESS FOR MAKING DIAMONDS [73] Assignee: The United States ofAmerica as represented by the Administrator of the National Aeronauticsand Space Administration [22] Filed: April 21, 1971 [21] Appl. No.:136,086

Related U.S. Application Data [62] Division of Ser. No. 3,418, Jan. 16,1970, Pat. No.

MAGNETI C HAMMER Primary ExaminerEdward J. Meros Attorney-L. D. Woffard,Jr. et al.

[57] ABSTRACT Apparatus and process for the production of diamond isdisclosed. The apparatus includes an exponential horn tapering from alarge end to a small end. A copper plate is mounted against the largeend of the horn and a magnetic hammer abuts the copper plate. Themagnetic hammer and copper plate function to create a shock wave in theexponential horn. An anvil having a small pocket formed therein ismounted adjacent to the small end of the exponential horn so that thesmall end rests in the pocket. The anvil, horn and hammer are allsecured together by bolts or other suitable means and, in operation,graphite is placed in the anvil pocket. The magnetic hammer generates ashock wave in the exponential horn and because of the horn shape, whichis critical, the velocity of the shock wave is amplified and the shockwave energy concentrated so that all of the energy in the shock wavearrives simultaneously at the small end of the horn. This energy istransferred to the graphite in the anvil pocket and results in pressureand temperature levels that causes the graphite to be transformed, inpart at least, to diamonds.

4 Claims, 3 Drawing Figures CAPACITOR 12 BANK VOLTAGE SOURCEPATENIEDJmiaomu h 3.714.332

l6 CAPACITOR BANK 38 VOLTAGE SOURCE MAGNETIC HAMMER 3o H" 34 300 Sec.

1mm V E; i. 5 I

LIJ a: l *0! TIME r V FIG. I

F l G. 2

JOHN R. RASQUIN MARVIN F. ESTES INVENTORS ATTORNEY ORIGIN OF THEINVENTION The invention described herein was made by an employee of theUnited States Government and may be manufactured and used by or for theGovernment for governmental purposes without the payment of anyroyalties thereon or therefor.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to the art of making industrial type diamonds and in particular,the invention is a simplified technique for making such diamonds with asimple, but effective apparatus. Industrial grade diamonds are a veryimportant item in the American economy as indicated by the fact thatindustrial diamonds have been classified by the United States Departmentof Defense as a special strategic material. There are two sources ofindustrial grade diamonds; those occurring naturally and obtained bymining, and synthetic diamonds. One application of industrial diamondsis in the making of diamond powder used in grinding wheels forsharpening sintered metal carbide cutting tools used in the metalworking industries and other industries wherein mass productiontechniques are utilized. Diamond powder is suspended in oil, water orgrease and used in polishing and lapping operations. A deficiency ofthese industrial diamonds could no doubt cause a serious slow down inthe modern metal working industry and possibly curtail the massproduction of many items. Better quality industrial diamonds are usedfor drills of various types ranging in size from large ones for drillingoil wells and the like to small precision type drills like those used bya dentist.

2. Discussion of Prior Art There have been many attempts in the past tomake synthetic diamonds and until recently such attempts met with littlesuccess. It was only within the last twenty-five or so years thatsynthetic diamonds have been made successfully. Principal efforts in thepast to make synthetic diamonds were by J. B. Hannay and Henri Moissan.In 1880 or thereabouts Hannay alledgedly made diamonds by heating amixture of hydrocarbons, hone oil and lithium at a red heat in sealedwroughtiron tubes. Thereafter around 1890 Moissan dissolved sugarcharcoal in molten iron and quenched the solution in cold water tocrystallize the carbon under the great internal pressures supposedlygenerated by contraction as the mass cooled. Efforts to repeat these twomethods have not met with success.

In 1955 the General Electric Company in Schenectady, New York,successfully made industrial grade diamonds by subjecting carbonaceousmaterials to pressures in excess of 1,500,000 pounds per square inch andsimultaneously to temperatures above 5,000F. Industrial diamonds weremade on a large scale by 1960 and up to one-tenth of a carat wasproduced in a single run. In this same general time frame diamonds weremade by a few other firms including the DeBeers Adamant Laboratory inJohannesburg, South Africa.

To date, diamonds of gem quality have not been made, but synthesizedindustrial diamonds have been found superior to natural diamonds for useas a grit in polishing compounds. This is because the synthetic diamondsare single crystals, roughly octahedral in shape with many cuttingedges. In making grit from naturally occurring diamonds it is necessaryto crush the diamonds and this crushing operation results in manyelongated slivers and flats which reduce the efficiency of the gritproduced.

A primary object of this invention is to provide a simplified techniqueand apparatus for the production of industrial grade synthetic diamonds.Synthetic diamonds are produced by the application of tremendous heatand pressure to carbon materials, but the equipment presently used togenerate this great heat and pressure is very massive and expensive. Thepresent invention can be made much simpler and smaller because itutilizes a greatly amplified shock wave to produce the necessarypressure. Since the pressure build-up is extremely rapid, enough heat isgenerated by the shock along with the pressure to result in theproduction of diamonds from graphite.

The apparatus employed includes an exponential horn ofsolid hardenedsteel that tapers from a large end to a small end. A magnetic hammer ispositioned adjacent the large end of the exponential horn with a copperplate positioned between the horn and magnetic hammer. An anvil having asmall pocket substantially equal in size to the small end of theexponential horn is arranged below the small end of the horn so that thesmall end fits into the pocket. Pure graphite to be converted intodiamonds is placed in .the pocket of the anvil andthen the hammer,copper plate, exponential horn and anvil are all secured together by asuitable supporting frame work.

The magnetic hammer is connected to a capacitor bank and voltage sourcethat delivers an electrical discharge in the form of a fast risingcurrent pulse for operating the hammer and generating a mechanical shockwave in the exponential horn that is directed to the graphite in theanvil. The shock wave generated in the large end of the exponential horntravels through the horn, and due to the shape ,of the horn, the shockwave is velocity amplified and concentrated so that substantially all ofthe energy in the shock wave arrives simultaneously in the small end ofthe horn contacting the graphite. As a result of this, a high speedpressure front is applied or transferred to the graphite which generatessufficient heat and pressure therein to convert a part of the graphiteto diamond grit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cross sectionedelevational view of an apparatus for practicing the invention;

FIG. 2 is a chart illustrating the shape of the current pulse applied tothe magnetic hammer; and

FIG. 3 is an enlarged view illustrating the arrangement of the small endof the exponential horn and the graphite in the anvil pocket.

DETAILED DESCRIPTION OF THE INVENTION The apparatus illustrated in FIG.1 consists of a magnetic hammer 10 connected to a capacitor bank 12 andvoltage source 14 through electrical transmission lines 16. The magnetichammer has a large coil in the lower end thereof (not shown) and acopper plate 18 is mounted in abutting relation to the lower end of themagnetic hammer. The copper plate and the hammer are separated by asheet of plastic material 20, mylar for example, to prevent any arcingthat might occur between the copper plate and the magnetic hammer duringthe operation of the apparatus. An exponential horn 22 is positionedimmediately below the copper plate. Horn 22 has a large end 24 thattapers down to a small end 26 that fits into a pocket 28 formed in ananvil 30. The horn is fabricated from extremely hard steel, preferably amaraging steel having a Rockwell hardness of 50.

The curvature of horn surface 23 is determined by the equation y=cewhere x and y are customary points on a plane defined by two coordinateaxes, c is a constant, e is the transcendal number used as the base ofthe system of natural logarithms, and a represents a constant. The shapeof the horn must exactly duplicate that shape which is obtained when theabove equation is, by appropriate mathematical manipulations,rotatedabout the x-axis to obtain a body of revolution. This shape is criticaland it has been found, as will be discussed hereafter, that even smallvariations in shape will result in a loss of efficiency in transmittingand concentrating the energy of the shock wave generated in the largeend of the horn. When diamonds are to be made, pure graphite 32 ispositioned in the pocket underneath the small end of the horn.

The apparatus is held together by means of two plates, lower plate 34and upper plate 36, the upper plate having a hole 38 formed in thecenter thereof for passage of electrical transmission lines from themagnetic hammer. The two plates are secured together by a plurality ofelongated rods 40 and 42 which are threaded at each end to accept nuts44. Any desired number of elongated rods could be used to assemble theapparatus, four being used in the apparatus shown and in the actualmodel successfully tested.

The operation of the device is as follows: assuming that the apparatushas been assembled in the manner shown in FIG. 1 and graphite has beenplaced in the pocket of the anvil. The capacitor bank is charged fromthe voltage source and an electrical discharge current pulse havingcharacteristics like that illustrated in the chart of FIG. 2, is appliedto the coil (not shown) of the magnetic hammer. The useful portion ofthe pulse or wave is the first 75 microseconds. The coil is positionedso as to be adjacent the copper plate. Magnetic hammers are knowndevices and one such hammer which is very similar to that used in thisapparatus is described in U. S. Pat. No. 3,360,972 issued on Jan. 2,1968. The discharge from the capacitor bank flows through the coil inthe magnetic hammer generating an intense magnetic field thereabouts.The magnetic field generated by the coil in the magnetic hammer inducespowerful eddy currents in copper plate 18 that are opposite in directionto the current in the coil of the magnetic hammer. The eddy currentsalso generate a strong magnetic field and the magnetic field developedby the eddy currents in the copper plate is such that it reacts againstthe magnetic field generated by the coil in the magnetic hammer. Ineffect the magnetic hammer and copper plate tend to be driven apart andwould in fact be driven apart if not held together by the supportingframe work discussed above. By utilizing an electrical discharge inwhich the rise time of the current pulse applied to the coil is veryrapid, the reaction just discussed will result in the generation of ashock wave in exponential horn 22. As the shock wave travels down thehorn it is velocity amplified and concentrated, due to the shape of thehorn, so that all of the energy arrives at the small end of the hornsubstantially simultaneously. The shock wave then leaves the horn andenters into the graphite. The shock wave entering the graphite is ineffect a very rapid pressure front which compresses and heats thegraphite sufficiently to promote the formation of diamonds from thegraphite.

In tests conducted with the apparatus, a small shock wave was firstgenerated to pack the graphite in the anvil pocket and then a secondshock wave was used to produce the diamonds.

Several test runs were made with the apparatus using different voltages.The capacitor bank employed had a capacity of 360 microfarads. Theenergy applied to the apparatus from the capacitor bank can bedetermined by the equation J /1- CV' where J is the energy in joules, Cis the capacitance in farads and V is the voltage applied to thecapacitor bank. The graphite was packed in each test run by a 1,000 voltdischarge and then a larger voltage was applied. When 3,000 volts wereused to charge the capacitor bank only yellow diamonds were produced.However, a 4,000 volt discharge resulted in diamonds that were abrighter yellow and at 5,000 volts clear diamonds were produced.

In the test using 5,000 volts a portion of the small end of theexponential horn was broken away. The horn was placed in a lath andsmoothed up so that it approached its original shape. However,subsequent tests employing high voltages resulted only in a low yield ofyellow diamonds. This leads to the conclusion that the shape of theexponential horn is critical.

The apparatus described herein could be utilized to make othercrystalline materials by replacing the gra phite with other materials.For example, sapphire could be made from aluminum oxide (Al What isclaimed is:

1. A method of making diamonds comprising the steps of:

' confining a predetermined amount of pure graphite in a pocket in ananvil, and

directing a pressure front into the graphitev by positioning anexponential horn having a large end and a small end, the shape of saidhorn being determined by the equation y=ce" so that the small end of thehorn is in contact with the graphite and generating a shock wave in thelarge end of the horn that is velocity amplified and concentrated sothat all of the energy in the shock wave arrives simultaneously at theend of the horn in contactwith the graphite whereby a pressure front istransferred to the graphite that compresses. and heats the graphite to alevel that promotes the formation of diamonds.

2. The method recited in claim 1 which further includes the step ofactuating a magnetic hammer to generate the shock wave in the horn.

3. A method of synthesizing diamonds from graphite comprising the stepof:

confining a quantity of graphite in a pocket in an angenerating a secondand more intense shock wave in vi], the large end of the horn thattravels through the positioflingatapered exponential horn b s s horn andis velocity amplified and concentrated end and a small the shape of hornbemg thereby to transmit a second pressure front to the determined bythe equation y=ce", so that the 5 small end thereof contacts thegraphite,

generating a first shock wave in the large end of the horn that travelsthrough the horn and is velocity amplified and concentrated thereby totransmit a pressure front to the graphite for settling the graphite inthe anvil pocket,

graphite that compresses and heats the graphite to a level that promotesthe formation of diamonds. 4. The method recited in claim 3 wherein amagnetic hammer is used to generate a shock wave in the ex- 10 ponentialhorn.

1. A method of making diamonds comprising the steps of: confining apredetermined amount of pure graphite in a pocket in an anvil, anddirecting a pressure front into the graphite by positioning anexponential horn having a large end and a small end, the shape of saidhorn being determined by the equation y ceax, so that the small end ofthe horn is in contact with the graphite and generating a shock wave inthe large end of the horn that is velocity amplified and concentrated sothat all of the energy in the shock wave arrives simultaneously at theend of the horn in contact with the graphite whereby a pressure front istransferred to the graphite that compresses and heats the graphite to alevel that promotes the formation of diamonds.
 2. The method recited inclaim 1 which further includes the step of actuating a magnetic hammerto generate the shock wave in the horn.
 3. A method of synthesizingdiamonds from graphite comprising the step of: confining a quantity ofgraphite in a pocket in an anvil, positioning a tapered exponential hornhaving a large end and a small end, the shape of said horn beingdetermined by the equation y ceax, so that the small end thereofcontacts the graphite, generating a first shock wave in the large end ofthe horn that travels through the horn and is velocity amplified andconcentrated thereby to transmit a pressure front to the graphite forsettling the graphite in the anvil pocket, generating a second and moreintense shock wave in the large end of the horn that travels through thehorn and is velocity amplified and concentrated thereby to transmit asecond pressure front to the graphite that compresses and heats thegraphite to a level that promotes the formation of diamonds.